feat(sandbox): add Python 3 code execution sandbox support

sandbox/app/middleware/__init__.py

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+"""Middleware package"""

sandbox/app/middleware/auth.py

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+"""Authentication middleware"""
+from fastapi import Header, HTTPException, status
+
+from app.config import get_config
+
+
+async def verify_api_key(x_api_key: str = Header(..., alias="X-Api-Key")):
+    """Verify API key from request header"""
+    config = get_config()
+    if x_api_key != config.app.key:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid API key"
+        )
+    return x_api_key

sandbox/app/middleware/concurrency.py

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+"""Concurrency control middleware"""
+import asyncio
+from fastapi import HTTPException, status
+
+from app.config import get_config
+from app.models import error_response
+
+
+# Global semaphores
+_worker_semaphore: None | asyncio.Semaphore = None
+_request_counter = 0
+_request_lock = asyncio.Lock()
+
+
+def init_concurrency_control():
+    """Initialize concurrency control"""
+    global _worker_semaphore
+    config = get_config()
+    _worker_semaphore = asyncio.Semaphore(config.max_workers)
+
+
+async def check_max_requests():
+    """Check if max requests limit is reached"""
+    global _request_counter
+    config = get_config()
+    
+    async with _request_lock:
+        if _request_counter >= config.max_requests:
+            raise HTTPException(
+                status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+                detail=error_response(-503, "Too many requests")
+            )
+        _request_counter += 1
+    
+    try:
+        yield
+    finally:
+        async with _request_lock:
+            _request_counter -= 1
+
+
+async def acquire_worker():
+    """Acquire a worker slot"""
+    if _worker_semaphore is None:
+        init_concurrency_control()
+    
+    async with _worker_semaphore:
+        yield